1. Field of the Invention
This invention relates generally to diaphragm valves and, in one particular embodiment, to a plastic body diaphragm valve having a pressure relief for use as a flush valve in a waste water system.
2. Technical Considerations
In most waste water systems, such as the flushing systems for urinals, commodes, and the like, the valves associated with these systems are traditionally metal valves. Metal valves provide strength for withstanding high-pressure fluctuations that may occur in the water pressure of the flushing system and also maintain their ability to function over prolonged and consistent use. However, these traditional metal flush valves do have some drawbacks. For example, these metal valves are typically relatively heavy and cumbersome to install and repair. Moreover, with continued use, metal valves may corrode or rust, and/or develop mineral deposits, which can require replacement of the entire valve. Additionally, such metal valves are typically expensive to manufacture and maintain.
Plastic valves are generally lighter in weight and less costly than metal valves and eliminate the corrosion associated with metal valves while reducing the development of mineral deposits. However, plastic valves are typically not as strong as metal valves. That is, plastic valves cannot typically withstand as high fluid pressures as metal valves without leaking or breaking. While plastic valves do exist, these known plastic valves are not capable of meeting the American Society Of Sanitary Engineering (ASSE) requirements for use in conventional waste water systems. For example, one ASSE requirement is that the valves in the waste water system must not leak at a fluid pressure of 500 psi or, if the valve incorporates a relief valve, the valve must hold two-times the relief pressure without leaking. Conventional plastic bodied valves cannot meet these limitations.
Additionally, many modern commodes and/or urinals are designed to operate most efficiently using a standard amount of water per flush, typically in the range of 1.5 to 2 gallons per flush. Therefore, known metal flush valves are designed to provide a selected amount of water per flush when new. However, with continued or prolonged use over time or as the internal components of the metal valve wear, it is not uncommon for these known metal flush valves to provide a different amount of water per flush than they were originally designed to provide. For example, a metal flush valve originally designed to provide 1.6 gallons per flush when new may eventually provide 2 or more gallons per flush due to valve component wear or use. For large applications, such as hospitals, prisons, apartment buildings, and the like, this can lead to an increase in water usage and cost. Additionally, these known flush valves cannot compensate for variations in water pressure during the flushing cycle that can also affect the amount of water per flush the valve provides.
Therefore, it would be advantageous to provide a flush valve that reduces or eliminates at least some of the problems associated with known flush valves. For example, it would be advantageous to provide a plastic body flush valve with a relief system that meets current ASSE requirement. It would likewise be advantageous to provide a flush valve that can provide a predetermined amount of water per flush despite valve wear and/or water pressure fluctuations.